Single mode optical waveguides (or optical fibers) are limited in bandwidth by dispersion. A pulse of given shape introduced into the input end of an optical waveguide will be spread as the pulse is transmitted along the length of the optical waveguide because of dispersion, the variation of wave phase velocity with wave frequency which is an inherent property of the materials comprising the guide as well as of guided modes themselves. For a particular waveguide with a given set of optical properties, the amount by which a pulse spreads is proportional to the length of the optical waveguide. Pulse spreading cannot be permitted to proceed to the point where adjacent optical pulses overlap. Thus, for a given pulse shape and optical waveguide, dispersion limits the length of the optical waveguide. Conversely, dispersion limits the pulse rate in an optical waveguide system having given optical waveguide properties and transmission distance.
Thus, there is a need in the art for optical waveguides and methods for fabricating them which reduce the amount of dispersion in an optical waveguide. Such dispersion-free optical waveguides would allow transmission of optical data signals over increased distances and at higher data rates relative to conventional optical waveguide systems which do not employ methods to reduce the dispersion in the optical waveguide. Moreover, there is a particular need in the art for an optical waveguide, and methods for fabricating them, having reduced dispersion and which do not require a predetermination of the length of the optical waveguide or its properties in order to properly compensate for the effects of dispersion.